Core i7 920 & DDR3 1333Mhz vs DDR3 1600Mhz OC Limits

Kenjineering

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Apr 5, 2009
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I am a layman.

Is it true that if I have DDR3 1333Mhz running with my core i7 920, that my max clock is around 3.5Ghz?
And that for DDR3 1600Mhz that my max clock is around 4.3 Ghz?





CPU: Core i7 920 @2.66Ghz (stock cooling)
Motherboard: Intel DX58SO "smackover"
Kingston DDR3 RAM 1333Mhz (matched with my CPU speed and currently at a miserable 1066mhz)
Gigabyte GTX280 SLI
Vista 64bit on Solid state.
 

foolycooly

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Dec 26, 2008
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well your memory speed is determined by your base clock and your ram multiplier. Let's assume you leave the cpu multiplier at the stock 20. For a 3.5 ghz overclock, you would need a BCLK of 175. Generally the lowest RAM multiplier available is 8x. Multiplying these two numbers gives us a RAM speed of 1400 (175 x 8). This is already over the rated speed on 1333 RAM. So, theoretically, yes, you are limited to about 3.5Ghz by using 1333 rated RAM. You might be able to push a bit higher depending on the overclockability of the set of RAM you have, but it could lead to instability.

In short, if you want to push 3.5 and above, buy 1600 ram.
 

Kenjineering

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Thanks for answering my question and giving me some scope on the issues involved. It really helped :)
 

rberry

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Jul 27, 2008
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I have corsair 1333 ram and got 3.8 with the ram o'c to 1520 at cas8.

Just showing that you do have options.

Standard 1.5 v and running it 1.6 v with not probs.
 

rorz

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Oct 17, 2009
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You dont have to buy 1600 RAM. You have to check what the limit of your motherboard is concerning RAM speeds. That is going to be your limit. In my case I have a Asus P6T and the OC limit for DDR3 RAM is 2000Mhz. Im running my 12GB of Kingston 1333Mhz Value RAM at 1600Mhz no problem, with RAM multiplier at 8x. To achieve this I used CPU Base clock 200Mhz with CPU multiplier of 17, giving me 3.4Ghz on my i7-920. Im using the intel stock fan too btw. All voltage settings set to Auto. My maximum CPU Temp reached 75 C after 1 hour of prime95. Memtest results were all successful too.